Semiconductors that detect light or other electromagnetic energy are called photo-detectors. There are several varieties including, but not limited to, optical detectors, chemical detectors, photoresistors, photovoltaic cells, photodiodes, and phototubes. Photo-detectors are used in a variety of applications including imaging. A specific type of photo-detector sensitive to the infra-red (IR) wavelengths of light is also known as an IR detector.
IR detectors are used in a variety of applications, and in particular in the military field where they are used as thermal detectors in night vision equipment, air borne systems, naval systems and missile systems.
The p-n junction is the foundation of semiconductors. It has been used as the basic building block for a wide variety of electronic and optoelectronic devices, such as diodes, transistors, optical detectors, and semiconductor lasers. It has been thought that a fundamental characteristic of the p-n junction is that it requires a depletion region, also known as a space charge region. The space charge region of conventional mid-IR detectors is a dominant source of defect-produced noise, also known as Shockley-Read-Hall (SRH) noise or generation-recombination (g-r) noise. This noise is produced by the creation of current carriers via thermal excitation through mid-gap defects in depletion regions. Fluctuations in g-r current are often the dominant source of noise in infrared photodiodes. G-r noise determines the amount of cooling required to reach background-limited-infrared-photodetection (BLIP) conditions in certain photodetectors. G-r noise can be reduced to minimal levels by cooling, but cooling is inconvenient and expensive, adds weight and bulk to the detector, and reduces the detector lifetime. If g-r noise could be eliminated, BLIP temperatures (TBLIP) of various photodetectors could be increased. An example of a TBLIP for a conventional photodetector is in the range of about 100° K. to about 120° K.
It is a primary object of the invention to provide a space-charge-free p-n junction in semiconductors. It is another object of the invention to provide p-n junctions having minimal or no g-r noise. It is a further object of the invention to provide p-n junctions that can function with increased TBLIP.